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| Titel |
Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic |
| VerfasserIn |
N.-X. Geilfus, R. J. Galley, O. Crabeck, T. Papakyriakou, J. Landy, J.-L. Tison, S. Rysgaard |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 6 ; Nr. 12, no. 6 (2015-03-31), S.2047-2061 |
| Datensatznummer |
250117886
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| Publikation (Nr.) |
 copernicus.org/bg-12-2047-2015.pdf |
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| Zusammenfassung |
Melt pond formation is a common feature of spring and summer Arctic sea ice,
but the role and impact of sea ice melt and pond formation on both the
direction and size of CO2 fluxes between air and sea is still unknown.
Here we report on the CO2–carbonate chemistry of melting sea ice, melt
ponds and the underlying seawater as well as CO2 fluxes at the surface of
first-year landfast sea ice in the Resolute Passage, Nunavut, in June 2012.
Early in the melt season, the increase in ice temperature and the subsequent
decrease in bulk ice salinity promote a strong decrease of the total
alkalinity (TA), total dissolved inorganic carbon (TCO2) and partial
pressure of CO2 (pCO2) within the bulk sea ice and the brine. As sea
ice melt progresses, melt ponds form, mainly from melted snow, leading to a
low in situ melt pond pCO2 (36 μatm). The percolation of
this low salinity and low pCO2 meltwater into the sea ice matrix
decreased the brine salinity, TA and TCO2, and lowered the in situ brine
pCO2 (to 20 μatm). This initial low in situ pCO2
observed in brine and melt ponds results in air–ice CO2 fluxes ranging
between −0.04 and −5.4 mmol m−2 day−1 (negative sign for
fluxes from the atmosphere into the ocean). As melt ponds strive to reach
pCO2 equilibrium with the atmosphere, their in situ pCO2 increases
(up to 380 μatm) with time and the percolation of this relatively
high concentration pCO2 meltwater increases the in situ brine pCO2
within the sea ice matrix as the melt season progresses. As the melt pond
pCO2 increases, the uptake of atmospheric CO2 becomes less
significant. However, since melt ponds are continuously supplied by meltwater, their in situ pCO2 remains undersaturated with respect to the
atmosphere, promoting a continuous but moderate uptake of CO2
(~ −1 mmol m−2 day−1) into the ocean. Considering the
Arctic seasonal sea ice extent during the melt period (90 days), we estimate
an uptake of atmospheric CO2 of −10.4 Tg of C yr−1.
This represents an additional uptake of CO2 associated with Arctic sea ice
that needs to be further explored and considered in the estimation of the
Arctic Ocean's overall CO2 budget. |
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